Lecture 6: Hippocampus, Amgydala and Frontal Cortex

Question 1

What is the only anatomical input into the limbic system and hippocampal complex

Answer 1

The olfactory bulb via the olfactory tract which branches at the olfactory trigone. No anatomical input into the hippocampal complex

Question 2

Compare the main functions of the hippocampus, amygdala, and Frontal cortex

Answer 2

Hippocampus is the gateway to memory formation and retrieval from long term storage

Amygdala is allocortex related to primal fright/flight/fight responses.

Frontal cortex is related to higher order thinking and value based decisions.

Question 3

Describe the pathway of the limbic system starting at the olfactory bulb

Answer 3

1. Olfactory bulb -> Olfactory trigone
2. a) Lateral amygdaloid complex (in temporal lobe; classic amgydala)
   b) Medial septal nuclei
   Both connected together by the Stria Terminalis (white matter).
3. From the MSN, –> Medial forebrain bundle/nigrostriatal pathway –> substantia nigra

Question 4

Describe the pathway of the hippocampal system starting at the Parahippocampal gyrus

Answer 4

1. Parahippocampal gyrus (archicortex) surrounding the
2. Dentate gyrus
3. Fornix
4. a) Post commisural arm–>Mamillary bodies
   b) Pre commissural arm–> Medial Septal nuclei
5. From the Mam. bod. goes the Mamillothalamic tract to the
6. Anterior Thalamic nucleus

Question 5

Explain the Papez’s circuit for memory formation and Memory recall

Answer 5

Memory formation
1. Dentate gyrus (classic hippocampus)
2. Fornix -> Mamillary body
3. Anterior thalamic nucleus
4. Cingulate gyrus - (relay between the hippocampus and frontal cortex)
5. Frontal cortex where it is manipulated and improved
Memory recall begins in the Frontal cortex and goes back to the
4. Cingulate gyrus
6. Parahippocampal Gyrus
1. Dentate gyrus

Question 6

Where is the hippocampal system and the limbic system connected, What is the purpose of this connection

Answer 6

The Medial septal nucleus, Hypothalamus which connects the mamilary body with the MSN which makes hormones/neurochemicals.

Connection allows the frontal cortex to alter primal behaviour with logical reasoning over time. If limbic system predominates can lead to anxiety, depression etc

Question 7

What is the other names for the MSN and what is its purpose

Answer 7

MSN aka Ventral striatum, Nucleus Accumbens

Looks after reward drive, reaction to instant satisfaction, addiction

Question 8

How does more dopamine influence the hippoc/limbic pathway and where does it come from/ go

Answer 8

Dopamine comes from substantia nigra and goes to the
a) MSN to increase reward drive; addiction susceptability

b) Striatum to increase movement initiation
b) Cingulate gyrus: help communication with Frontal cortex can lead to loss of executive function

Question 9

How does more norepinephrine influence the hippoc/limbic pathway and where does it come from/ go

Answer 9

1. NE made in the Locus Coerulus in the brain stem
2. Goes into Anterior Thalamic nucleus, hypothalamus and cingulate gyrus
3. It keeps those neurons firing appropriately.
   It is an antidepressant in form of re uptake inhibitors, keeping mood even.

Question 10

How does more serotonin influence the Papez pathway and where does it come from/ go

Answer 10

1. Serotonin made in Raphe nucleus in brainstem.
2. Goes to the Cerebellum, Spinal cord, Anterior Thalamic nucleus, hypothalamus, Cingulate Gyrus.
3. It alters how much the frontal cortex can affect the Amygdala and MSN (limbic cortex) and vice versa. It helps boosting the frontal thinking over primal thinking.